Radiative and opacity data obtained from large-scale atomic structure calculations and from statistical simulations for the spectral analysis of kilonovae in their photospheric and nebular phases: the sample case of Er III

• Published in: The European physical journal. D, Atomic, molecular, and optical physics Atomic, molecular, and optical physics, 2024-08, Vol.78 (8), Article 105
• Main Authors: Deprince, Jérôme, Carvajal Gallego, Helena, Ben Nasr, Sirine, Maison, Lucas, Pain, Jean-Christophe, Palmeri, Patrick, Quinet, Pascal
• Format: Article
• Language: English
• Subjects: Applications of Nonlinear Dynamics and Chaos Theory; Atomic; Atomic physics; Atomic Spectra and Oscillator Strengths (ASOS14); Atomic structure; Context; Ejecta; Emission analysis; Erbium; Hartree approximation; Kilonovae; Line spectra; Molecular; Neutron stars; Opacity; Optical and Plasma Physics; Photosphere; Physical Chemistry; Physics; Physics and Astronomy; Quantum Information Technology; Quantum Physics; Regular Article; Relativistic theory; Spectroscopy/Spectrometry; Spectrum analysis; Spintronics; Star mergers
• ISSN: 1434-6060; 1434-6079
• DOI: 10.1140/epjd/s10053-024-00897-5

This study is an overview of the atomic data and opacity computations performed by the Atomic Physics and Astrophysics Unit of Mons University in the context of kilonova emission following neutron star mergers, in both the photospheric and nebular phases. In this work, as a sample case, we focus on a specific lanthanide ion, namely Er III. As far as the LTE photospheric phase of the kilonova ejecta is concerned, we present our calculations using both a theoretical method (the pseudo-relativistic Hartree-Fock method, HFR) and a statistical approach (the Resolved Transition Array approach, RTA) to obtain the atomic data required to estimate the Er III expansion opacity for typical conditions expected in kilonova ejecta one day after the merger. In order to draw the limitations of both of our strategies, the results obtained using the latter are compared, and a calibration procedure of the HFR atomic data in this context is also discussed. Concerning the kilonova ejecta nebular phase, atomic parameters that characterize forbidden lines in Er III are calculated using HFR as well as another computational approach, namely the Multiconfiguration Dirac–Hartree–Fock (MCDHF) method. The potential detection of such lines in late-phase kilonova spectra is then discussed. Graphical abstract